A method and apparatus for performing block sequential processing is
described. In one embodiment, the apparatus comprises a determine pass
logic, selection logic, next coefficient logic and control. The determine
pass logic has inputs coupled to receive significance state information
for a region, a pass bit for each coefficient in a subset of the region,
and a current pass indication. In response to these inputs, the determine
pass logic generates pass indications to indicate a pass for each
coefficient in the subset of the region. The selection logic has inputs
coupled to signals output from the determine pass logic and the current
pass indication and, in response to these inputs, generates output
indications associated with one pass of either the significance
propagation, refinement, and cleanup passes. The next coefficient logic
is coupled to the selection logic and indicates the next coefficient in
the current pass in response to the output indications from selection
logic. The control is coupled to receive the output indicating the next
coefficient in the one pass and codes coefficients in the significance
propagation, refinement and cleanup passes. The control also codes the
next coefficient in either the significance propagation, refinement and
cleanup passes as indicated by the next coefficient logic.